Here is how it works.
If you are now on DENIM and install the insider app on your phone and enroll in the program you will be able to get the windows 10 technical preview update.
If you want to roll back then you need to use the Windows Software Recovery Tool to roll back and you will roll back to DENIM. And as long as you do not use the insider app again you are "out" the W10 TP update circle.

If you now are on CYAN + preview for developer and you enroll in the W10 TP and you roll back with the Windows Software Recovery Tool you will roll back to CYAN only so you will "loose" the preview for developers OS updates. Or it could be that you roll back to DENIM if DENIM was released while you where on W10 TP.

Here is how it works.
If you are now on DENIM and install the insider app on your phone and enroll in the program you will be able to get the windows 10 technical preview update.
If you want to roll back then you need to use the Windows Software Recovery Tool to roll back and you will roll back to DENIM. And as long as you do not use the insider app again you are "out" the W10 TP update circle.

If you now are on CYAN + preview for developer and you enroll in the W10 TP and you roll back with the Windows Software Recovery Tool you will roll back to CYAN only so you will "loose" the preview for developers OS updates. Or it could be that you roll back to DENIM if DENIM was released while you where on W10 TP.